Mechanism for Migration and Layer Growth of Biomass Ash on Ilmenite Used for Oxygen Carrier Aided Combustion
Journal article, 2018

Biomass is recognized as a CO2-neutral energy resource. However, biomass is a challenging fuel to combust because of its heterogeneity with regard to the content of inorganic constituents, volatiles, and moisture. Oxygen carrier aided combustion (OCAC) is a process advancement that provides enhanced combustion in existing circulating fluidized bed (CFB) units. The oxygen carrier has a central role in the OCAC concept through the oxygen transport it provides. The natural mineral ilmenite (FeTiO3) has been identified as a promising potential oxygen carrier. In order to ensure the feasibility even for long-term operation in industrial-scale processes, it is imperative to understand the evolution of the material during an OCAC process. In the present study, ilmenite was used as the bed material in the Chalmers 12 MWth CFB boiler during OCAC with woody biomass as fuel. Bed material samples were extracted from the bed inventory at different time intervals ranging from 5 to over 300 h. This paper proposes a mechanism for migration and layer growth of biomass ash on the ilmenite used as the oxygen carrier in a CFB combustor. It was found that with increased time of exposure, potassium migrated into the particle core. Longer process times led to the formation of a calcium layer around the particle, and simultaneously, migration of calcium inward on the particle was observed. Thermodynamic calculations were used along with analysis techniques in order to build a hypothesis for the possible mechanism of ash-bed material interaction.

Author

Angelica Corcoran

Chalmers, Space, Earth and Environment, Energy Technology

Pavleta Knutsson

Chalmers, Chemistry and Chemical Engineering, Energy and Material, Environmental Inorganic Chemistry

Fredrik Lind

Chalmers, Space, Earth and Environment, Energy Technology

Henrik Thunman

Chalmers, Space, Earth and Environment, Energy Technology

Energy & Fuels

0887-0624 (ISSN) 1520-5029 (eISSN)

Vol. 32 8 8845-8856

Subject Categories

Chemical Process Engineering

Bioenergy

Other Materials Engineering

DOI

10.1021/acs.energyfuels.8b01888

More information

Latest update

12/5/2018